1. Field of the Invention
The present invention relates to an audio disc of improved data structure, particularly relates to an audio disc having a higher packing density than a regular CD's (Compact Disc), of which the data format of DVD (Digital Video Disc) system is utilized, and relates to a reproduction apparatus for the audio disc.
2. Description of the Related Art
A CD is well known as an optical disc for reproduction of audio signal such as music, and a DVD disc is also known as an optical disc of higher packing density than CD's. A DVD disc is widely used for recording video information, and this kind of DVD disc is hereinafter called a DVD-Video disc. A video signal is recorded on a DVD-Video disc as a main information and an audio signal is recorded as a sub-information thereon. Therefore, many problems are associated with an audio part of the DVD disc such as; less recording capacity for the audio signal due to a composite signal scheme of audio and video signals, no time management of audio signal, not retrievable character information even a simple word like a title of music.
Furthermore, for users of audio apparatus who, in comparison with users of video apparatus, prefer to a simpler reproduction method, a TOC (Table Of Contents) area is provided on a DVD-Video disc like a CD. However, a DVD-Video disc comprises video contents block units including a (control pack (CONT Pack), plural video packs (V Pack) and audio packs (A Pack). Since the CONT Pack controls the reproduction of V and A Packs, it is rather hard to record audio signals mainly, when the audio signals are reproduced simply.
Moreover, in the DVD-Video disc, the timing of audio signal is controlled only by a video frame. On the other hand, time management of audio signal is controlled on a sampling frequency basis, so that audio signals are hardly arranged in video frames without having extra spaces or bytes. In some cases, a discontinuity of audio signal requires to fill extra spaces with blank data. Therefore, it is hard to manage actual playback timing of audio signal, when recording audio signals mainly is intended.
In addition thereto, although DVD-Video discs and reproduction apparatuses of DVD-Video disc are currently available in a market and the reproduction apparatus can reproduce music CDs and video CDs as well as DVD-Video discs, a reproduction apparatus which can reproduce a variety of DVD discs as well as DVD-Audio disc being recorded with audio signals mainly is desirable for users.